<!DOCTYPE html>
<html lang="zh-CN">
    <head>
        <meta charset="UTF-8" />
        <title>弹性盒子瓜分空白</title>
        <style>
            .outer{
                width: 1000px;
                height: 615px;
                border:5px dashed red;
                display: flex;
            }
            .item{
                width: 200px;
                height: 200px;
                border:1px solid black;
                background-color: aqua;
            }
            .item1{
                flex-grow: 1;
            }
            .item2{
                flex-grow: 1;
            }
            .item3{
                flex-grow: 2;
            }
        </style>
    </head>
    <body>
        <div class="outer">
            <div class="item item1"></div>
            <div class="item item2"></div>
            <div class="item item3"></div>
        </div>
    </body>
</html>